The present invention relates to a molding machine, and more particularly to a feed assembly for a molding machine that simultaneously provides a repeatable predetermined volume of each of a multiple of fluid material components.
Many molding machines provide for the mixing of at least two fluid materials to form a hardenable or settable mixture which can be discharged into a mold cavity in the formation of an article molded of synthetic resin. The fluid materials commonly include at least two reactive components, e.g. isocyanates and polyols in the molding of polyurethanes or epoxide resins and amine hardeners in the molding of epoxies. Other settable mixtures can include three components such as a catalyst, a matrix polymer and a foaming agent.
A multiple of the fluid materials are typically fed from a supply by a delivery or feed assembly which communicates with a mixing head. Each fluid material is mixed by the mixing head and discharged into the mold cavity to form the molded article.
An important aspect of the molding process is the quantity of each fluid material that is supplied to the mixing head during each cycle of the molding machine. Each fluid material must be simultaneously feed in the correct quantity to the mix head to assure the correct composition of the finished material. Each fluid material must also be repetitively supplied in correct metered quantities during each cycle of the molding machine to maintain the consistency of each molded article. It is further desired to supply the metered quantities over the shortest period of time to improve productivity of the molding process.
The rapid discharge multiple material delivery molding system according to the present invention generally includes a feed assembly having an upper portion, a movable middle portion and a lower portion. A drive is mounted between the middle portion and the lower portion to drive the middle portion along guide posts to simultaneously control the intake and discharge of a fluid material from each of a plurality of fluid delivery container.
Each fluid delivery container generally includes a fluid cylinder attached between a packing assembly, a lower mounting assembly and a port assembly which includes an inlet port and an outlet port. Although a cylinder is illustrated in the disclosed embodiment, it should be realized that other container shapes will benefit from the present invention. Importantly, the fluid cylinder is specifically sized to contain a predetermined volume of fluid material. By attaching a plurality of variously sized fluid delivery containers to the lower portion, an exact volume of each fluid material is dispensed simultaneously upon a downward stroke of the middle portion.
Each inlet port communicates with a fluid material supply while each outlet port communicates with a mix head. Valves located in each fluid port control the flow of the fluid material in response to movement of the middle portion. Each valve can be connected to a controller and preferably operated pneumatically.
As the drive strokes the middle portion, the valve in each inlet port is opened while the valve in each outlet port is closed. Accordingly, when the middle portion reaches the top of its stroke, each fluid cylinder is filled. Because the fluid cylinder has been previously sized to contain only a measured quantity of fluid material, the system is assured of providing the correct ratio of each fluid material during each cycle. The drive is then reversed to drive a piston rod into each fluid cylinder. The fluid material in each fluid delivery container is now discharged to the mix head where the correct predetermined volume (due to the sized fluid cylinders) reaches the mix head simultaneously (due to each piston rod being linked to the middle portion). A correct mix of fluid material is thereby assured to reach the mix head. In other words, the flow of each component per unit time maintains the correct ratio. An effective final material and thus a consistent molded article is assured.
In one embodiment a pump is located along each conduit between each fluid material supply and the feed assembly. The pumps assist in filling each fluid cylinder during the upward stroke of the middle portion.
In another embodiment, at least some of the material supplies are individually pressurized to assist in filling each fluid cylinder while avoiding the use of pumps. Pressurizing each fluid material supply is particularly desirable when a delicate fluid material is being dispensed. It is further preferred that all the conduits which supply the fluid material are only gently curved and ninety degree bends are particularly avoided. These two aspects are particularly beneficial with the polymer matrix being moved to the mix head which is an inventive material as also invented by applicant wherein the matrix carries glass fibers. Preferably, the glass fibers are enclosed in a protective coating (silicone and/or epoxy). The coating prevents the fiber from beginning to react. In the mix head, the coatings are smashed and the fibers can begin to react. However, the pressure supply and curved conduits avoid the coatings from being smashed until it reaches the mix head.
The present invention therefore provides a molding machine that simultaneously provides a repeatable predetermined volume of each of a multiple of fluid material components.
The disclosed system is particularly valuable when used to move the several components for molding large items to a mix head and then a mold. In one application the mold is forming large tub and shower surrounds.